1. Field of the Invention
The present invention relates to a liquid crystal projector.
2. Description of the Background Art
As light sources for liquid crystal projectors, a metal halide lamp, an extra-high pressure mercury lamp, etc. have been used. The lamps significantly increase in temperature when they are driven. Accordingly, cooling fans have been generally used for the liquid crystal projectors.
The cooling fan is a source of noise. In the recent trend to quiet sound, the cooling fan has been operated in the vicinity of the lower limit of an operation assurance voltage (the minimum voltage at which the rotation of a fan can be maintained after the fan is rotated once) to drive the fan in a state where the number of revolutions is reduced as much as possible, thereby suppressing noise produced from the fan.
However, the minimum voltage required to rotate a fan from a state where the fan is stopped (the minimum voltage for fan starting) is higher than the operation assurance voltage. Accordingly, the minimum voltage for fan starting which is higher than the operation assurance voltage is applied to the cooling fan when the power to the liquid crystal projector is turned on, and the applied voltage is lowered after the fan is started, to achieve quiet sound. Consequently, noise produced by the fan is low at the time of normal operation, while high noise is produced at the time of starting.
Since the minimum voltage for fan starting which is determined in the specification is set to a voltage higher than a voltage required to actually rotate the cooling fan from a state where the cooling fan is stopped, the cooling fan is actually started at a voltage lower than the minimum voltage for fan starting which is determined in the specification.